SPOILER ALERT: This blog is for those who are watching season six of Lost. Don't read on if you haven't seen episode nine – and if you've seen more of the series, please be aware that many UK viewers will not have done …

"You're dead. We're all dead. We're not on an island. We're in hell."

"Ab aeterno"

Well, that's that then. Shall we all go home? (No, not you, Not-Locke!). A pretty unequivocal answer for once in Lost's long and winding tale. But was it? Richard (or Ricardo as he used to be called) is pretty certain about the true nature of the island – but is he just seeing it through his 1867 eyes? "It's an island. I see the devil!" But is it too literal an explanation for what's actually going on? Was he just talking about his own immortal hell – the other people who won't give him a straight answer after all these years? Or are the writers getting in one last nod to the much-denied purgatory theory that my fellow Lost In Lost blogger Steve Busfield still loves? When I interviewed Carlton Cuse and Damon Lindeloff last year, they specifically denied it! Have they been playing a Jacob-like game with us, knowing that it's not purgatory but a few floors down?

There's no denying that this was an episode packed with religious symbolism – both explicitly in scenes like the priest refusing to absolve Ricardo of his accidental murder, and the burying of Isabella's cross, and also more subtly with Jacob plunging Richard into the ocean for another impromptu Lost baptism. I couldn't help wishing I'd boned up on Paradise Lost - I'm sure it's been mentioned, but it suddenly struck me that maybe that's the key text after all? (Well, that and Star Wars – as others have suggested.) The whole idea of free will v predestination, good v evil, has never been spelled out more clearly than in this epic episode: it wouldn't be too much of a stretch to have Smokey as a Satan-like fallen angel messing with Jacob the heavenly father, would it? Especially with lines like: "I wanted them to help themselves." (It would make me laugh if the title sequence carried on for a few seconds more in the last episode, to include the word "Paradise …" on that final black screen).

I've been thinking of that old Ben line: "We're the good guys, Michael." But is it really as simple as Jacob being good, and Smokey being bad? Obviously, the man dressed in black is being positioned on the dark side here – but the way that Jacob has been bringing in groups of people over the years, killing off people he's not interested in (whether it's the tailees on Oceanic 815, or the rest of the slaves on the Black Rock), is a pretty harsh way to test your belief in humanity.

No time for the Sideways universe this week. We had a few moments on the beach with Team Jacob trying to work out what to do next; a glimpse into Ilana's bedside visit from Jacob to set up Richard's story ("he'll know what to do next") – and then one huge flashback, all the way back to 1867 and the start of Richard/Ricardo's epic journey from Tenerife to the beach. No wonder he never looks fazed.

As Steve mentioned last week, there's been some great focus on individual characters in this last season – and it felt like a treat to get this much back story from Richard, one of the most enigmatic characters in the whole show. Not only did we find out how he has avoided ageing – the touch of Jacob again – but we also found out why. If you're doomed to spend eternity in hell, just live forever, and you'll escape it. Simple. Like so many of the actors playing out the final scenes, Nestor Carbonell rose to the occasion. It's not easy to pull off the trick of playing someone who's been dealing with Jacob's game for the past 140-odd years, but this was moving, revelatory stuff.

Cameo of the week

• Great to see the Black Rock in action, and to find out that it was behind the destruction of Tawaret's statue.

• Cap'n Magnus Hanso! Nice detail about the ship's crew there – did hope we'd get a sighting of this Hanso Foundation ancestor!

The grand alliance count

Think we're pretty much where we left everyone at the end of play last week.

Polar bear sightings

Hang on, do you get polar bears in hell? Nice horse, though.

Quotes of the week

• "It's good to see you out of those chains." Not-Locke clearly has a good memory – anyone else get that "ah, so that's what he meant!" shudder when he said this to Ricardo, echoing their later conversation on the beach?

• "There's only one way to escape from hell – you're going to have to kill the devil." MIB again. How long before this appears on a Lost T-shirt?

• "The cork is this island – keeping darkness where it belongs." Did anyone else wonder what Jacob's wine tasted like? Looked like a Pinot to me …

• "It's not exactly Locke." Even when he's just hanging out around a fire, Ben manages to cut to the heart of the matter.

• "We all go to hell!" That's some pretty good motivation.

Notes and predictions

• Jacob told Ilana that Richard would know what to do. He said he didn't have a clue. But will he now he's had a word with his wife Isabella via Hurley's Spirits-R-Us ghostworld connection? Or is Hurley going to be stepping up? Loved how he brushed Jack off when he was talking to invisible Isabella on the beach.

• Another close up on an eye – this time, Richard's (and his heavy, heavy eyelashes).

• When Not-Locke said to Richard "he took my body, he took my humanity", was it true?

• The Black Rock and the white pebble. Another one of Jacob's grand cosmic jokes?

• Will we ever get a name for Not-Locke? Love how it nearly slipped out this episode, but then he fobbed Richard off by describing himself as "a friend". Yup, Melvin it is.

• The episode title "Ab aeterno" seems to translate variously as "from eternity", "from the everlasting" or "from the beginning of time". However you cut it, you get the point that this game has been going for longer than the six seasons we've been watching it.